Experimental study of unsteady wake effect on a film-cooled pitchwise-curved surface

Mahadevan, Srikrishna and Kutlu, BF and Golsen, MJ and Verma, SB (2015) Experimental study of unsteady wake effect on a film-cooled pitchwise-curved surface. International Journal of Heat and Mass Transfer, 83. pp. 118-135. ISSN 0017-9310

PDF ja556post.pdf Restricted to Registered users only Download (7MB) | Request a copy

Abstract

Unsteady wake interactions with the near wall flow field occur when a surface is exposed to fluid flow past upstream rotating bodies. In the case of gas turbines, understanding such interactions are essential to better design cooling schemes on endwalls. In view of this, an experimental study has been conducted to determine the heat transfer coefficient and film cooling effectiveness on a pitchwise-curved surface which is subjected to unsteady passing wakes generated using a wake rod in a wall-normal orientation. The mainstream Mach number was maintained approximately constant at 0.03. A single row of cylindrical film holes with pitch to diameter ratio of 3 and inclined at 35� to the test surface are used for discrete film injection. The coolant to mainstream mass flux ratio (M) is varied between 0.25 and 1. A spoke-wheel type wake generator is used to produce unsteady wakes at two wake Strouhal numbers (S = 0.15, 0.3). Measurements are made for (i) steady mainstream flow (S = 0) which serves as a baseline case, (ii) mainstream flow with unsteady wakes, (iii) steady mainstream flow with film injection (iv) both (ii) and (iii) combined. The unsteady passing wakes mitigated jet lift-off at high coolant to mainstream momentum flux ratios. The maximum increase in film effectiveness was measured to be ffi16.35% at the jet centerline for M = 0.75, S = 0.3 at x/D = 2. At high coolant to mainstream mass flux ratios, a combination of increasing film jet turbulence and strong interaction with the mainstream, deteriorates film cooling effectiveness but increases the heat transfer coefficient. Heat transfer augmentation increased by ffi7.6% for the highest wake passing frequency (S = 0.3) without film injection. A combination of unsteady passing wakes and film injection resulted in a maximum pitch-averaged and centerline heat transfer augmentation of ffi28% and 31.7% respectively.

Item Type:	Article
Additional Information:	Copyright to this article belongs to M/s. Elsevier Science
Uncontrolled Keywords:	Unsteady passing wake;Wall-normal wake rod;Film cooling effectiveness;Heat transfer augmentation;Pitchwise-curved surface;Jet lift-off;Jet-to-jet interaction
Subjects:	AERONAUTICS > Aeronautics (General) AERONAUTICS > Aerodynamics
Depositing User:	Ms. Alphones Mary
Date Deposited:	24 Jul 2015 09:55
Last Modified:	24 Jul 2015 09:55
URI:	http://nal-ir.nal.res.in/id/eprint/12252

Actions (login required)

View Item